PERRY, Ga. -- Marines are training for the "what-if" scenario that keeps counter-terrorism experts up at night - an attack on a major American city. They're at a facility nicknamed "The Disaster Disneyland," CBS News correspondent Mark Strassmnan reports.
Imagine this: terrorists have detonated a 10-kiloton nuclear bomb in downtown Indianapolis. There are 17,000 casualties. Specially-trained Marines have pushed inside a five-mile "hot zone" of radiation that rings the city.
"Our first priority is to save lives," said Colonel Stephen Redifer. "So give me the toughest mission that you have, densest population, and we'll immediately begin dragging those casualties out."
Redifer leads 200 Marines in a special unit called CBIRF: Chemical Biological Incident Response Force.
"We possess unique capabilities that allow us to go into a contaminated environment, be it chemical, biological, radiological, or just simply a large conventional explosion," Redifer said.
The Marines triage civilians and can process 250 people an hour in decontamination tents. They also clear roads for other response forces that will follow. Sometimes it's easy to forget this is a training exercise.
"I think this is about as real as it gets," Redifer said.
The training takes place at Guardian Centers, an 830-acre training complex built on the grounds of a former missile plant. The miniature city has a one-mile, four-lane highway and a simulated downtown with 60 buildings of all sizes.
"You have to plan and you have to train," said Geoff Burkart. "Hope is not a plan."
Burkart founded Guardian Centers three years ago. He got the idea when he saw the immediate response to Katrina - one disaster following another.
"An agency, an army will perform under great stress," Burkart said. "They'll perform to their lowest level of conditioned training. So the higher you can raise that bar, the better the response."
People hired to play the wounded look like they strolled off the set of "The Walking Dead." One actress plays a pregnant woman going into labor.
"Live role players give you an aspect of free-play training that just doesn't exist with mannequins or dummies or anything," Redifer said. "They're going to respond differently. They're going to act differently, they're real people."
The greatest test for Colonel Redifer's Marines occurs when they arrive downtown.
"The biggest challenge in this scenario is just the sheer size of it," Redifer said. "We have to go in and cover and search every single floor, every single building, every single closet, and it is just exhausting."
But Redifer knows that the training is not just useful, it's necessary.
"It's readiness, readiness, readiness," he said. "Because we can't predict when this is going to happen."